How To Use the WNetUseConnection API to Map a Drive in Visual Basic

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Article ID: 256847 - View products that this article applies to.
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This article demonstrates how to use the WNetUseConnection API function to map a system-supplied drive letter to a network share. In addition, the WNetCancelConnection2 API function is demonstrated to show how to disconnect a mapped drive.


At times, it is necessary to map a drive letter to a network share. There are several API functions that can be used to accomplish this, such as WNetAddConnection, WNetAddConnection2, WNetAddConnection3, and WNetUseConnection. The primary difference is that with the WNetUseConnection function, you do not need to specify the drive letter to be used, while it is required with the other API functions.

Steps to Create Sample

  1. Create a new Standard EXE project in Visual Basic. Form1 is created by default.
  2. Add three TextBox controls to Form1 and name them txtUNC, txtUser, and txtPWD.
  3. Set the PasswordChar property of txtPWD to an asterisk (*).
  4. Add two CommandButtons to Form1 and set their Captions to CONNECT and DISCONNECT.
  5. Paste the following code into the code window of Form1:
    Option Explicit
    Private Const NO_ERROR = 0
    Private Const CONNECT_LOCALDRIVE = 256
    Private Const CONNECT_REDIRECT = 128
    Private Const RESOURCE_GLOBALNET = &H2
    Private Const RESOURCETYPE_DISK = &H1
    Private Const CONNECT_UPDATE_PROFILE = 1
    Private MappedDrive As String
    Private Type NETRESOURCE
        dwScope As Long
        dwType As Long
        dwDisplayType As Long
        dwUsage As Long
        lpLocalName As String
        lpRemoteName As String
        lpComment As String
        lpProvider As String
    End Type
    Private Declare Function WNetUseConnection Lib "mpr.dll" _
       Alias "WNetUseConnectionA" ( _
       ByVal hwndOwner As Long, _
       ByRef lpNetResource As NETRESOURCE, _
       ByVal lpUsername As String, _
       ByVal lpPassword As String, _
       ByVal dwFlags As Long, _
       ByVal lpAccessName As Any, _
       ByRef lpBufferSize As Long, _
       ByRef lpResult As Long) _
       As Long
    Private Declare Function WNetCancelConnection2 Lib "mpr.dll" _
       Alias "WNetCancelConnection2A" ( _
       ByVal lpName As String, _
       ByVal dwFlags As Long, _
       ByVal fForce As Long) _
       As Long
    Private Sub Command1_Click()
       Dim NetR As NETRESOURCE    ' NetResouce structure
       Dim ErrInfo As Long        ' Return value from API
       Dim buffer As String       ' Drive letter assigned to resource
       Dim bufferlen As Long      ' Size of the buffer
       Dim success As Long        ' Additional info about API call
       ' Initialize the NetResouce structure
       NetR.dwScope = RESOURCE_GLOBALNET
       NetR.dwType = RESOURCETYPE_DISK
       NetR.lpLocalName = vbNullString
       NetR.lpRemoteName = txtUNC.Text
       ' Initialize the return buffer and buffer size
       buffer = Space(32)
       bufferlen = Len(buffer)
       ' Call API to map the drive
       ErrInfo = WNetUseConnection(Me.hWnd, NetR, txtPWD.Text, txtUser.Text, _
          CONNECT_REDIRECT, buffer, bufferlen, success)
       ' Check if call to API failed. According to the MSDN help, there
       ' are some versions of the operating system that expect the userid
       ' as the 3rd parameter and the password as the 4th, while other
       ' versions of the operating system have them in reverse order, so
       ' if first call to API fails, try reversing these two parameters.
       If ErrInfo <> NO_ERROR Then
          ' Call API with userid and password switched
          ErrInfo = WNetUseConnection(Me.hWnd, NetR, txtUser.Text, _
             txtPWD.Text, CONNECT_REDIRECT, buffer, bufferlen, success)
       End If
       ' Check for success
       If (ErrInfo = NO_ERROR) And (success = CONNECT_LOCALDRIVE) Then
          ' Store the mapped drive letter for later usage
          MappedDrive = Left$(buffer, InStr(1, buffer, ":"))
          ' Display the mapped drive letter
          MsgBox "Connect Succeeded to " & MappedDrive
          MsgBox "ERROR: " & Str(ErrInfo) & " - Connect Failed!"
       End If
    End Sub
    Private Sub Command2_Click()
       Dim ErrInfo As Long     ' Return value from API
       ' Call API to disconnect the drive
       ErrInfo = WNetCancelConnection2(MappedDrive, _
       ' Check for success
       If ErrInfo = NO_ERROR Then
          MsgBox "Disconnect of '" & MappedDrive & "' Succeeded"
          ' Clear the mapped drive letter
          MappedDrive = ""
          MsgBox "ERROR: " & Str(ErrInfo) & " - Disconnect Failed!"
       End If
    End Sub
  6. Save and run the sample.
  7. In the first TextBox, type the UNC path to the share you wish to map to a drive letter (such as, \\ServerName\ShareName).
  8. In the second TextBox, type your network logon name.
  9. In the third TextBox, type your password.
  10. Click the CONNECT button.

    RESULT: Provided you have typed a valid user id, password, network share, and have the appropriate network permissions, you should receive a message indicating that the share was connected and the mapped drive letter is given. You can verify the map by opening the Windows Explorer.
  11. Click the DISCONNECT button.

    RESULT: The mapped drive is disconnected. Again, this can be verified with the Windows Explorer.


For additional information on creating network connections with API calls from Visual Basic, click the article number below to view the article in the Microsoft Knowledge Base:
173011 How To Add and Remove Network Connections


Article ID: 256847 - Last Review: August 30, 2004 - Revision: 2.2
  • Microsoft Visual Basic 6.0 Learning Edition
  • Microsoft Visual Basic 6.0 Professional Edition
  • Microsoft Visual Basic 6.0 Enterprise Edition
  • Microsoft Visual Basic 5.0 Control Creation Edition
  • Microsoft Visual Basic 5.0 Learning Edition
  • Microsoft Visual Basic 5.0 Professional Edition
  • Microsoft Visual Basic 5.0 Enterprise Edition
  • Microsoft Visual Basic 4.0 Standard Edition
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  • Microsoft Visual Basic 4.0 32-Bit Enterprise Edition
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